Organic thin films have been heavily investigated in recent years due to their application in optoelectronic devices such as organic light emitting devices (OLEDs), photovoltaic devices and organic photodetectors.
Optoelectronic devices based on organic materials, including organic thin films, are becoming increasingly desirable in a wide variety of applications for a number of reasons. Materials used to construct organic optoelectronic devices are relatively inexpensive in comparison to their inorganic counterparts, thereby providing cost advantages over optoelectronic devices produced with inorganic materials. Moreover, organic materials provide desirable physical properties, such as flexibility, permitting their use in applications unsuitable for rigid inorganic materials.
Light emitting polymeric species, for example, have found general acceptance in various lighting applications, such as consumer electronic devices. While finding general acceptance, however, current light emitting polymeric species have several disadvantages limiting their application in certain fields. Similar to inorganic light emitting diodes comprising crystalline semiconductors, light emitting polymeric species have relatively narrow emission bands, thereby precluding white light emission from single polymeric species. As a result, organic light emitting devices are often constructed of a series of polymeric species having the desired emission profiles that, when combined, provide white light emission from the device.
Various light emitting polymeric species can be physically combined in several ways to provide a source of white light emission. In one construction, individual light emitting polymeric species are provided in a layered format. In one embodiment, for example, a layer of red light emitting polymer is combined with a layer of green light emitting polymer and a layer of blue emitting polymer to provide white light emission. Layering individual polymeric species to achieve white light emission has the inherent disadvantage of creating multiple interfaces in the device, thereby increasing the likelihood of device failure due to interfacial instability between the layers.
An alternative construction using multiple light emitting polymeric species is to blend the polymeric species to provide white light emission. Red light emitting, green light emitting and blue light emitting polymeric species, for example, can be blended into a single layer for achieving white light emission. Blending polymeric species also has inherent disadvantages that can lead to premature device failure. Polymeric blends are susceptible to spinodal decomposition over time and various operating conditions resulting in lost device performance or device failure.